Push-pull valve for gas sampling bags

Abstract

A push-pull valve for gas sampling is formed by assembling a body including a receptacle having a bore and a plug having a nose which seats in the bore. The plug has a through bore with a shoulder at its lower end serving as a lower stop and defining a hole at the bottom of the through bore. A hollow stem slides in the through bore, between an extended, closed position, and a retracted, open position. The stem has ports set above the foot of the stem a distance such that, in an upper position of the stem, the port is blocked by an O-ring, and in a lower position of the stem, gas can flow through the stem, the ports, an annular space around the stem, and out through the hole at the bottom of the through bore.

I claim: 
     
       1. A push-pull valve for installation in an aperture in a wall of a gas sampling bag, said valve comprising a body including a receptacle adapted to engage one side of the wall and having a bore and a plug having a nose which seats in the bore when the plug is inserted into the receptacle through the aperture from an opposite side of the wall, the plug having a through bore with a shoulder at its lower end serving as a lower stop and defining a hole at the bottom of the through bore,   a hollow stem having a sliding fit in said through bore and being axially movable in the bore between an upper position and a lower position, said stem having a foot at its lower end which engages said shoulder in the lower position of the stem,   an O-ring disposed in an annular space defined between said receptacle bore and said stem,   said stem having at least one lateral port set above said foot a distance such that, in the upper position of the stem, the port is blocked by the O-ring, and in the lower position of the stem, gas can flow through the stem, the ports, the annular space and the hole at the bottom of the through bore into the bag.   
     
     
       2. The invention of claim 1, wherein the valve further comprises a septum through which one can insert a syringe needle to contact the contents of the bag. 
     
     
       3. The invention of claim 1, wherein each of the receptacle and plug has a brim, and each brim has a hole through it, said holes being aligned during assembly of the valve, and at least one of said holes containing a septum which can be pierced by a syringe needle. 
     
     
       4. The invention of claim 3, wherein the hole in the brim of the receptacle has a counterbore, and the septum is installed in said counterbore. 
     
     
       5. The invention of claim 4, wherein the counterbore faces the brim of the plug, so that the septum is captured in the counterbore by the plug when the valve is assembled.